All electrical or electrochemical devices in operation are the source of losses of energy that are manifested in the form of heat. Miniaturization, notably of items of electronic equipment, combined with the increase in dissipated power, require an increasingly elaborate thermal design of these devices in order to keep the temperature of the components in their range of operating tolerances. Outside certain temperature limits, their performance is mediocre or even totally lacking. Moreover, certain items of equipment must operate in hot and sunny climates and do this without making use of sources of external active cooling. The evacuation of heat is therefore a crucial problem, each element or device having to be kept at its nominal operating temperature. Thus, faced with the increase in the thermal power dissipated per unit of surface area, there is currently a need for compact and robust systems making it possible to absorb the peaks of thermal load so that the items of equipment do not exceed the maximum admissible temperatures. These systems are called thermal dissipation systems.
There are currently many solutions based essentially on active cooling systems: mini heat pump operating according to a refrigeration cycle, chamber with water circulation with or without change of phase, fan, thermoelectric module, etc. Microjets of air or of water droplets are instead dedicated to the cooling of the components and not of the systems.
Despite the performance that they provide, these devices nevertheless have the following drawbacks. Most of these devices require an external energy source, they are relatively bulky or even noisy and their miniaturization proves to be fragile and often accompanied by a deterioration in their efficiency.
Passive operation based on solid/liquid phase-change materials (abbreviated to PCM) (paraffins, etc.) is currently experiencing strong growth, but mainly in the fields of construction and industrial processes. Their effectiveness is however limited due to the moderate value of the latent heat (approximately 180 J/g) and above all because the melting temperature cannot be controlled in dynamic operation. Specifically, it depends on the PCM material used. PCMs damp down the temperature variations but they are above all well suited to the very large and large systems for which the constraints of volume or of weight are limited or even nonexistent.